REFRIGERANT > ON-VEHICLE INSPECTION

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1. INSPECT REFRIGERANT PRESSURE WITH MANIFOLD GAUGE SET


  1. This method uses a manifold gauge set to locate problem areas. Read the manifold gauge pressure when these conditions are established. Test conditions:

    1. Temperature at the air inlet is 30 to 35°C (86 to 95°F).
    2. Engine is running at 1,500 rpm.
    3. All doors are fully open.
    4. Blower speed control switch is at HI.
    5. A/C switch is ON.
    Gauge readings (Reference).


    I030081E04




      E050573E01
    1. Normally functioning refrigeration system

      Gauge reading:
      Pressure side
      Refrigerant volume
      Low
      0.15 to 0.25 MPa (1.5 to 2.5 kgf/cm2)
      High
      1.37 to 1.57 MPa (14 to 16 kgf/cm2)


    2. The A/C system periodically changes between normal and improper function due to moisture in the refrigerant system.


      I022117E16


      Symptoms
      Probable Cause
      Diagnosis
      Corrective Actions
      During operation, pressure on low pressure side cycles between normal and vacuum
      Moisture in refrigeration system freezes at expansion valve orifice, causing temporary stop of cycle. However, when melted, normal state is restored.
      - Drier is overly saturated
      - Moisture in refrigeration system freezes at expansion valve orifice and blocks refrigerant circulation
      1. Replace cooler drier
      2. Remove moisture from cycle by repeatedly evacuating air
      3. Supply appropriate volume of new refrigerant


    3. The A/C system does not function effectively due to insufficient cooling.


      I022118E09


      Symptoms
      Probable Cause
      Diagnosis
      Corrective Actions
      - Pressure low on both low and high pressure sides
      - Cooling performance insufficient
      Gas leakage from refrigeration system
      - Insufficient refrigerant
      - Refrigerant leakage
      1. Check for gas leakage and repair if necessary
      2. Supply appropriate volume of new refrigerant
      3. If indicated pressure value close to 0 when connected to gauge, create vacuum after inspecting and repairing the location of leakage


    4. The A/C system does not function effectively due to poor circulation of the refrigerant.


      I022119E10


      Symptoms
      Probable Cause
      Diagnosis
      Corrective Actions
      - Pressure low on both low and high pressure sides
      - Frost exists on piping from condenser to A/C unit
      Refrigerant flow obstructed by dirt in condenser
      Condenser clogged
      Replace condenser


    5. The A/C system does not function intermittently because the refrigerant does not circulate.


      I022120E09


      Symptoms
      Probable Cause
      Diagnosis
      Corrective Actions
      - Vacuum indicated on low pressure side, and extremely low pressure indicated on high pressure side
      - Frost or condensation seen on piping on both sides of condenser or expansion valve
      - Refrigerant flow obstructed by moisture or dirt in refrigeration system
      - Refrigerant flow obstructed by gas leakage from expansion valve
      Refrigerant does not circulate
      1. Check expansion valve refrigerant
      2. Clean expansion valve by blowing air
      3. Replace condenser
      4. Evacuate air and charge appropriate volume of new refrigerant
      5. For gas leakage from expansion valve, replace expansion valve


    6. The A/C system does not function effectively due to overcharged refrigerant or insufficient cooling of the condenser.


      I022121E10


      Symptoms
      Probable Cause
      Diagnosis
      Corrective Actions
      Pressure extremely high on both low and high-pressure sides
      - Excessive refrigerant
      - Cooling performance of condenser insufficient
      - Condenser is dirty
      - Condenser fan motor is malfunctioning
      - Excessive refrigerant
      1. Clean condenser
      2. Check condenser fan motor operation
      3. If 1 and 2 normal, check the amount of refrigerant and supply appropriate volume of refrigerant


    7. The A/C system does not function due to air in the refrigeration system.

      CAUTION:
      The low-pressure piping may be very hot and cause serious burns.


      I022122E03


      Symptoms
      Probable Cause
      Diagnosis
      Corrective Actions
      - Pressure extremely high on both low and high-pressure sides
      - Low-pressure piping is too hot to touch
      Air in refrigeration system
      - Air in refrigeration system
      - Vacuum purging insufficient
      1. Check if compressor oil is dirty or insufficient
      2. Evacuate air and charge new refrigerant


    8. The A/C system does not function effectively due to an expansion valve malfunction.


      I022123E11


      Symptoms
      Probable Cause
      Diagnosis
      Corrective Actions
      - Pressure extremely high on both low and high-pressure sides
      - Frost or condensation on piping on low-pressure side
      Problem with expansion valve
      - Excessive refrigerant in low pressure piping
      - Expansion valve too wide open
      Replace expansion valve


    9. The A/C system does not function due to a defective compressor.


      I022124E10


      Symptoms
      Probable Cause
      Diagnosis
      Corrective Actions
      - Pressure extremely high on both low and high-pressure sides
      - Pressure extremely low on high pressure side
      Internal leakage in compressor
      - Compression failure
      - Leakage from damaged valve or broken sliding parts
      Repair or replace compressor